Study of the development and evolution of seasonal thermocline and turbulent processes in the northern parts of Persian Gulf using numerical modeling

The Persian Gulf (PG) is a semi-enclosed shallow sea which is connected to open ocean through the Strait of Hormuz. Thermocline as a suddenly decrease of temperature in subsurface layer in water column leading to stratification happens in the PG seasonally. The forcing comprise tide, river inflow, solar radiation, evaporation, northwesterly wind and water exchange with the Oman Sea that influence on this process. In this research, analysis of the field data and a numerical (Princeton Ocean Model, POM) study on the summer thermocline development in the PG are presented. The Mt. Mitchell cruise 1992 salinity and temperature observations show that the thermocline is effectively removed due to strong wind mixing and lower solar radiation in winter but is gradually formed and developed during spring and summer; in fact as a result of an increase in vertical convection through the water in winter, vertical gradient of temperature is decreased and thermocline is effectively removed. Thermocline development that evolves from east to west is studied using numerical simulation and some existing observations. Results show that as the northwesterly wind in winter, at summer transition period, weakens the fresher inflow from Oman Sea, solar radiation increases in this time interval; such these factors have been caused the thermocline to be formed and developed from winter to summer even over the northwestern part of the PG. The model results show that for the more realistic monthly averaged wind experiments the thermocline develops as is indicated by summer observations. The formation of thermocline also seems to decrease the dissolved oxygen in water column due to lack of mixing as a result of induced stratification. Over most of PG the temperature difference between surface and subsurface increases exponentially from March until May. Similar variations for salinity differences are also predicted, although with smaller values than observed. Indeed thermocline development happens more rapidly in the Persian Gulf from spring to summer. Vertical difference of temperature increases to 9 centigrade degrees in some parts of the case study zone from surface to bottom in summer. Correlation coefficients of temperature and salinity between the model results and measurements have been obtained 0.85 and 0.8 respectively. The rate of thermcline development was found to be between 0.1 to 0.2 meter per day in the Persian Gulf during the 6 months from winter to early summer. Also it is resulted from the used model that turbulence kinetic energy increases in the northwestern part of the PG from winter to early summer that could be due to increase in internal waves activities and stability intensified through water column during this time.

Effect of temperature on genomic and some biological indices during embryonic and larval development of Caspian trout Salmo trutta caspius Kessler, 1877

Since 1966 especially recent decade, Caspian trout (Salmo trutta caspius Kessler, 1877) considered as a strategic endemic species for Caspian Sea fisheries resources also coldwater aquaculture in Iran. Nowadays habitat condition effects on this subspecies during life stages, artificial breeding and incubation period noticed by research and execution sessions of fisheries in Iran. Incubation duration of Caspian trout from artificial fertilization followed by green egg and eyed egg, hatching and yolk sac absorption identified as most sensitive stages for fish and any pollution, stress and deviation by natural life conditions of embryo up to larvae could provide possible mortalities and observable or hidden alterations. Among all vital factors for Caspian trout welfare even in conservation plans and stocks rehabilitation programs or recent attempts for domestication of this fish for introduction to cold water aquaculture industry, water temperature as the most important physical factor which might conserve or induce stress to rearing environment condition is not considered yet. In hatcheries activities, the temperature for incubation and rearing Caspian trout eggs is determining by available water temperature and wide range of temperatures in governmental or private farms is using depend on the water resources availability. Also global climate change consideration and increase temperature trend accompany with group of physical and chemical factors provided by fish farm discharges and other source points entered to the migration pathway of Caspian trout in spawning season were not investigated before. Natural spawning migration pathway is upstream of Caspian tout south and south west rivers especially in Cheshmehkileh upstream in Tonekabon, Iran directed this research focus on the mentioned location. For simulation of natural spawning bed for Caspian trout, water supplied from the upstream of Daryasar branch as headwater of Cheshmehkileh River which provided REDD water condition for in vitro incubation. Green eggs treatments of wild and F1 cultured brooders both 3+ were incubated. Incubation implemented in dark, constant temperature (4, 8, 12 degree centigrade) and DO–pH–temperature digital monitoring in 3 recycling incubators ended to yolk sac absorption and entering larval stage. Hatching success, possible genome alterations by HSP70 gene expression and comet assay implemented as diagnostic tools in 3 life stages of eyed egg– Alevin and Larvae. Numbers and diameters of larvae white fiber muscles measured by histology experiment and Hematoxylin–eosine staining. Results stated significant effect of incubation temperature on hatching success, genome and white fiber muscles of wild and F1 samples. Hatching success measured as 31% and 38% for cultured and wild cold treatments, 79% and 91% for normal and 64% and 73% for warm cultured and wild treatments respectively. Considerable mortality occurred for cold treatment and 8 degree centigrade stated the best thermal condition in normal incubator according to hatching success in wild Caspian trout samples.